Osteoclast cytomorphometry in patients with femoral neck fracture

In patients with femoral neck fracture, nutritional deficiencies have been shown to be common. A low calcium diet and/or a reduced vitamin D intake have been suspected to cause secondary hyperparathyroidism responsible for increased bone turn over and bone loss. Parathyroid hormone (PTH) levels are increased in these patients, data which are in accordance with the pronounced changes observed on bone biopsies reflecting a true hyperparathyroidism. We have used a cytomorphometrical approach to characterize PTH-induced changes on the osteoclastic population. Osteoclasts were detected histochemically (by tartrate resistant acid phosphatase staining) on bone biopsies from 10 control subjects, 8 patients with primary hyperparathyroidism and 10 patients with a femoral neck fracture of osteoporotic origin. The maximum Feret's diameter of each osteoclast (Oc.Le) was determined with a semiautomatic image analyzer. In all groups, the frequency distribution of Oc.Le appeared positively skewed. In both hip fractured patients and primary hyperparathyroid patients, the mode of the distribution was higher (25-30 microns) than in controls (20-25 microns). When graphically converted on a probability graph, the osteoclastic populations appeared homogeneous and well described by a lognormal distribution in the three groups. However, osteoclasts appeared similarly enlarged in the groups of patients with primary hyperparathyroidism and with femoral neck fracture. PTH has been shown to increase both the recruitment of mononucleated precursors and their fusion into larger osteoclasts than controls. In the present study, a cytomorphometric method appeared able to identify the border line hyperparathyroidism in the hip fractured patients.